Nontraumatic prosthetic valve with magnetic closure

ABSTRACT

An improved valve prosthesis for causing non-traumatic unidirectional flow of a pulsatory fluid, such as blood, through a conduit, such as a blood vessel by means of magnetic force. The valve may include two flaps, made of a suitable flexible material, attached by the proximal ends to opposite sides of a covered annular mounting structure. A pair of magnetic members are connected to the distal ends of the flaps thereby to exert either repulsive or attractive force to permit the smooth, non-traumatic closure of the valve flaps. If repulsive force is used, the opposite sides are prevented from impacting traumatically. In another embodiment a pair of rigid flaps are mounted for pivotal movement along a common diametrical line and prevented, by magnetic repulsive force, from impacting traumatically in either the closed or open positions.

TECHNICAL FIELD

The present invention relates generally to an improved valve forcontrolling the unidirectional flow of a pulsatory fluid and, morespecifically, to a valve prosthesis which provides for the nontraumaticcontrol of body fluid flow, such as blood flow through the heart of ahuman or animal by use of magnetic repulsive force.

BACKGROUND ART

Artificial valves, both those used as prosthetic devices within thehuman and animal body and those used to control the flow of body fluidsexternally, have long been known to the medical profession. The priorart valves used primarily as prosthetic devices have taken many forms inan attempt to replicate the function of the natural valves which theyreplace. None of these prior art valves, however, has fully achieved thereplication of a naturally occurring valve. Lack of success has resultedin part from problems with long term durability of the valve itself andfrom differences between actual and measured fluid flow area provided bythe valve which has resulted in undesirable pressure gradients acrossthe valve. In addition, prior art valves increase, rather than reduce oreliminate, the turbulence created by the passage of the fluid throughand the subsequent closure of the valve. Such turbulence results ingreatly increased hemolysis when the fluid flowing through the valve isblood.

Prior art prosthetic valves conform, for the most part, to three generaltypes. The ball and cage valve, such as that described in U.S. Pat. No.3,416,159, is illustrative of one type. The valve ball, usuallyconstructed of silicone rubber, is susceptible to variance in shape,fractures of the ball surface and subsequent lipid infiltration into theball. Additional complications which often accompany this type of valveinclude fibrin clot formation, which further interfers with the movementof the ball in the cage, and thrombosis. Because of these complications,the patient with this type of prosthesis must undergo continuousanticoagulant therapy. Moreover, since the ball portion of the valvemust be located in the center of the cage to allow proper functioning ofthe valve, fluid flow through this type of valve cannot be central, asin a natural valve, but is directed through the valve around theperiphery of the ball. The turbulence resulting from this, coupled withthe turbulence created by closure of the valve, causes a higher level ofhemolysis and blood cell damage than is desirable. The presence of theball in the center of the blood vessel also imparts an unnatural radialcomponent to the flow of blood within the vessel producing injury to thewalls of the vessel against which the radial component is directed. Balland cage valves are large in size and therefore can present difficultiesin insertion. They have also been disturbing to some persons into whomthey have been inserted because of the audible sound detectable uponclosing. Attempts to correct the deficiencies of the ball and cage typevalve by replacing the ball with a disc shaped element have generallybeen unsuccessful.

A second type of prior art valve, generally referred to as a tissuevalve, is composed of a stent or mounting ring to which human or animaltissue has been attached in a form which approximates the flaps in anatural valve. However, the long-term durability of these valves isstill a matter of concern. Construction of the tissue valve from cadavermaterial such as fascia lata results in a valve with low durabilitybecause of rapid tissue degradation and stiffening and has led to tissuedysfunction and subsequent valve immobility. While another variation ofthe tissue valve, the glutaraldehyde-fixed porcine xenograft,illustrated by U.S. Pat. No. 4,084,268 to Ionescu et al, has not been asprone to these problems, degradation and calcification of the tissuematrix resulting in valve dysfunction have been reported. Moreover,Johnson et al in The Journal of Thoraic and Cardiovascular Surgery75:599-605, 1978, concluded that functional stenosis or narrowing of theblood vessel was commonly encountered when the porcine xenograft wasused to replace the aortic valve. Moreover, since these valves relyentirely on back pressure for closure, closure is accompanied byincreased trauma to the blood cells and the greater likelihood of valveincompetence than encountered with a natural valve.

U.S. Pat. Nos. 3,197,788 to Segger and 3,736,598 to Bellhouse et aldescribe prosthetic cardiac valves that are similar to tissue valves intheir structure, but are made of flexible synthetic materials. Bothvalves disclosed in U.S. Pat. Nos. 3,197,788 and 3,736,598 imitate thenatural valve by providing three cusps or flaps, which comprise thevalve members, attached to a supporting ring. The valves open inresponse to the pressure exerted on them during systole and close inresponse to the back pressure exerted on the flaps during diastole.However, this closure is quick and somewhat traumatic and enhances thelikelihood of increased turbulence and subsequent damage to the bloodcells.

A third category of prosthetic valve is the disc type, which isgenerally formed of an annular base to which a disc-shaped valvingmember is secured, either by means of a magnetic hinge, as in U.S. Pat.No. 3,370,305 to Goott, by means of an eccentrically-placed stem, as inthe Modified University of Capetown Prosthesis described by Ellis et al,in The Annals of Thoracic Surgery 23:26-31, 1977, or by means of a rodalong which the disc can be displaced, as in U.S. Pat. No. 3,959,827 toKaster. Although fluid flow through this type of valve is morecentralized than through the ball and cage valve, increased hemolysisresults from turbulence created by fluid flow through the valve. Inaddition, injury to the walls of the blood vessel beyond the valveresults from the radial components imparted to the blood flow caused bythe presence of the valve disc in the blood stream. Moreover, use ofthis valve necessitates the institution of long-term anticoagulanttherapy because of the high level of thrombogenesis which accompaniesthe use of the valve. As reported in The Annals of Thoracic Surgery23:26-31, 1977, Ellis et al discontinued use of one type of tilting discprosthesis, in part because of the excessive incidence ofthromboembolism and in part because the effective valve orifice areaafter the valve had been in place was usually considerably less than themeasured orifice area before insertion.

In U.S. Pat. No. 3,959,827, Kaster discloses one embodiment of a disctype valve in which the closing of the valve is assisted by means of apermanent magnet located in the disc valving member. Although thispermits a smoother closing than is possible without the magnet, the discvalve disclosed in U.S. Pat. No. 3,959,827 still suffers from the otherdrawbacks generally common to disc type valves. Forman et al reported inThe Journal of Thoracic and Cardiovascular Surgery 75:595-598, 1978,that they no longer recommended the use of a tilting disc valve similarto the one disclosed in U.S. Pat. No. 3,959,827, in large part becauseof a high incidence of embolism and valvular thrombosis, but alsobecause the effective orifice area of the valve was less than the actualorifice area. In addition, they found this type of valve demonstrated noclear hemodynamic advantage over other available prostheses.

Valves used for medical purposes in which valve closing is magneticallyassisted are disclosed in U.S. Pat. Nos. 3,233,610 to Wade, 3,495,620 toRaimondi et al and 3,926,175 to Allen et al. The valves described inU.S. Pat. Nos. 3,233,610 and 3,495,620 provide fluid flow orificesthrough only a portion of the valve diameter, thus resulting in a slowfluid flow area in relation to valve diameter. The magnetically actuatedvalve disclosed in U.S. Pat. No. 3,926,175 is incapable of operating inresponse to fluid pressure within a body vessel and is thus unable tooperate automatically to cause unidirectional flow of a pulsatory fluid.Magnetic repulsive forces have been used to aid valve operation asillustrated in U.S. Pat. No. 3,476,355 to Sherwood but has never beenused to prevent traumatic valve operation which could result in injuryto body fluids.

DISCLOSURE OF THE INVENTION

It is a general object of this invention to overcome the deficiencies ofthe prior art relating to artificial and prosthetic valves as discussedabove.

It is a more specific object of this invention to provide an improvedvalve for producing unidirectional flow of a pulsatory fluid through aconduit and, more specifically, to provide an improved prosthetic valvefor the nontraumatic control of the flow of body fluids through humanand animal vessels.

It is an object of the present invention to provide a prosthetic valvewith good hemodynamic characteristics, a valve that provides lessobstruction of the valve orifice area than prior art valves when fullyopen and a valve that is competent when shut. More particularly, thevalve of the present invention provides a valve structure comprises ofan annular mounting structure to which is attached at their proximalends two opposed, spaced flexible flaps, which flaps include at theirdistal ends magnetic members with sufficient magnetic force to preventtraumatic closure and to reduce the systaltic pressure required uponopening.

It is another object of the present invention to provide a prostheticvalve characterized by a greater satisfactory operating life, comparedto previously known valve designs, during which the valve will notdegenerate or wear out and will be free from variance. The valve of thepresent invention is constructed of durable synthetic materials which,in combination with the novel structure, fulfill the stated objectives.

It is a further object of the present invention to provide a prostheticvalve that does not significantly alter blood components and causes onlyminimal hemolysis. The novel structure of the present invention may haveflexible flaps which include magnetic members at their distal ends,which flaps are closed gently during diastole by a combination of thepressure gradient and the repulsive force between the magnets. Suchclosure is rapid, but smooth, and eliminates the turbulence andsubsequent hemolysis characteristics of prior art valves.

It is another object of the present invention to provide a prostheticvalve that is antithrombogenic, thus eliminating the need for thelong-term administration of anticoagulants and their attendantcomplications. The novel structure of the present invention includes nosurfaces upon which fibrin clots are likely to form and, in addition,may be constructed of a synthetic fabric widely used for arterialgrafts, the use of which specifically contra-indicates anticoagulanttherapy.

Other objects of the present invention include providing a prostheticvalve which can be inserted into a body conduit without undue difficultyand which does not disturb the person or animal into which it isinserted, such as by making an audible noise upon closing. The annularmounting structure can be made in sizes to conform to the internaldiameters of the vessels into which it is to be inserted. Additionally,the flexible synthetic material of the flaps is used to cover themounting ring, thus providing a means of easily suturing the valve tothe vessel. The soft, nontraumatic closing of the flaps of the presentinvention assisted by the attractive forces exerted by the magnets inthe distal ends of the flaps in quiet and avoids disturbance to theperson or animal in which the valve is implanted.

Additional objects, advantages and features of the invention will bemore readily apparent from the following detailed description of apreferred embodiment of the invention when taken together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing in perspective of one embodiment of the valve of thepresent invention in a closed position;

FIG. 2 is a cross-sectional view of the valve taken along lines 2--2 ofFIG. 1;

FIG. 3 is a cross-sectional view of the valve of FIG. 1 showing itlocated within a conduit in the open position;

FIG. 4 is a cross-sectional view of the valve of FIG. 1 showing itlocated within a conduit in the closed position;

FIG. 5 is a drawing in perspective of a second embodiment of the presentinvention;

FIG. 6 is a drawing in perspection of a third embodiment of the presentinvention;

FIGS. 7A & B are elevational views of the valve orifice of a fourthembodiment of the present invention with the valve in a closed and openposition, respectively;

FIG. 8 is a cross-sectional view of a natural heart valve;

FIGS. 9A-9C are cross-sectional view of various known prosthetic heartvalve designs; and

FIG. 10 is a prospective view of an additional embodiment of the subjectinvention in which magnetic repulsive force is used to prevent traumaticimpact of the movable valve elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, FIGS. 1 through 4 depict different views ofthe same embodiment of the present invention. The improved valve of thepresent invention, generally referred to as 10, includes an annularmounting structure or mounting ring 12, which may be made of either arigid or semi-flexible material such as plastic. The outside diameter bof the annular mounting structure 12 will be determined by the diameterof the conduit or body vessel into which the valve of the presentinvention is to be inserted.

The annular mounting structure 12 is connected with one end of a tube 16formed from a flexible, nonresilient biologically non-reactive fabric.The internal diameter "a" of central tube 16 should be equal to orslightly less than the outside diameter "b" of annular mountingstructure 12. The axial length "c" of central tube 16 will depend on theparticular application of the valve of the present invention.

As can now be appreciated from a consideration of FIGS. 1-3, tube 16constitutes a tubular element which forms a type of valve outlet meansfor moving from a first configuration (FIG. 1) in which fluid flowthrough the valve is cut off to a second configuration (FIG. 3) in whichfluid may freely flow through the valve in response to the fluidpressure upstream of the valve increasing above the fluid pressuredownstream of the valve. Each 14 of tube 16, attached to mountingstructure 12, is designed to be placed upstream in a body fluid conduitthrough which one way flow of body fluid is desired. End 14 of tube 16is retained in a constantly open condition by mounting structure 12while the opposite end 17 of flexible tube 16 is left unsupported and isthus held in a closed position (FIGS. 1-2) whenever the fluid pressureP₁ upstream of the valve falls below the downstream pressure P₂. Upon areversal of the relative magnitudes of P₁ and P₂, end 17 of tube 16 isforced open as illustrated in FIG. 3 to allow fluid flow through tube16.

As illustrated in FIGS. 1 and 3, valve 10 is equipped with closureassistance means 19 for applying a continuous force to opposite sides(or wall segments) of tube end 17 to bias the valve toward the openand/or closed position as illustrated in FIGS. 1 and 2. The magnitude ofthe bias force produced by means 19 is relatively weak and thus therelative difference in the upstream pressure P₁ and the downstreampressure P₂ needed to open and close the valve are changed onlyslightly.

Closure assistance means 19 includes a pair of flaps 18 and 20 attachedat their proximal ends 22 and 24, respectively, to opposite sides ofannular mounting structure 12. Flaps 18 and 20 are constructed of thesame flexible fabric as tube 16 and terminate short of end 17 of tube16, as shown in FIG. 1. Alternatively, flaps 18 and 20 may extend beyondend 17 of tube 16 or may be the same length as tube 16. Closureassistance means 19 also includes permanent magnetic members 28 and 30exerting either a mutually attractive force on one another to create aclosing force or a mutually repulsive force to prevent a traumaticclosure. To prevent decomposition caused by body fluids, magneticmembers 28 and 30 may be encased within the fabric which forms flaps 18and 20 or may be covered with an inert material and then attached to thedistal ends of flaps 18 and 20. Flaps 18 and 20 may be attached only toannular mounting structure 12 at their proximal ends 22 and 24 oradditional points of attachment to central tube 16 may be providedanywhere along the length of flaps 18 and 20, for example, at thelocation of magnetic members 28 and 30.

FIG. 2 illustrates the valve of FIG. 1 in the closed position as itappears in bottom elevational view through the valve orifice, generallyshown at 32. The opposed sides of the tube end 17 meet along a line 34as seen in FIG. 2 when the pressure P₁ is sufficiently greater thanforce P₂ to bring the opposed sides (or wall segments) of members 28 and30 together.

In FIGS. 3 and 4, the improved valve 10 of the present invention isshown in cross-section view as it appears when inserted within a fluidconduit 36, such as a blood vessel. FIG. 3 shows valve 10 in an openposition as results when upstream pressure P₁ has exceeded thedownstream pressure P₂ sufficiently to open the valve. The fluid flow,represented by arrow 38, which follows the opening of tube end 17,maintains the magnetic members 28 and 30 in a spaced apart positionuntil upstream pressure P₁ again decreases in magnitude to cause theopposed sides to close. If magnetic members 28 and 30 are arranged tocreate an attractive force therebetween, as discussed further inapplication Ser. No. 6,027 filed Jan. 24, 1979, now U.S. Pat. No.4,245,358, the magnetic attractive force of members 28 and 30 issufficient to move the opposite sides of tube end 17 into the closedposition illustrated in FIG. 4. With this arrangement, it is apparentthat the disclosed valve does not rely solely upon back pressure tocause valve closure. Rather, the disclosed closure assistance means 19,in the form of a pair of permanent magnetic members 28 and 30, is ableto effect valve closure before the build up of any significant backpressure which would tend to bring the exposed sides of tube end 17 intoviolent contact.

As noted above, member 28 and 30 may be arranged to create a mutuallyrepulsive force to prevent traumatic impact of the opposed sides of thevalve upon a sufficient change in the relative upstream and downstreampressure. Although not illustrated in FIGS. 1-4, the use of repulsiveforce magnetic elements would require flaps 18 and 20 to be attached, atleast in the central section, to corresponding sections of oppositesides (or wall segments) of tube 17. If repulsive force is used toimplement the subject invention, very little force tending to maintainthe valve open is created between members 28 and 30 when the valve isopen (FIG. 3) due to the relatively large distance between members 28and 30. Thus, only a slight increase in downstream pressure P₂ over theupstream pressure P₁ is required to effect closing motion of the valve.As the opposed valve elements near the condition illustrated in FIG. 4,the repulsive force between members 28 and 30 will increase in aproportional manner to prevent traumatic impact between the opposedsides of the valve. The operation of the repulsive force embodiment ofthis invention differs from the operation of the attractive forceembodiment by relying solely on the upstream/downstream pressuredifferential to effect valve closure and by relying on magneticrepulsive force to cushion the impact upon closure of the valveelements. In the attractive force embodiment, the magnetic attractiveforce is used to effect more rapid closure before the pressuredifferential has time to increase to a level which is sufficient tocause traumatic impact.

FIGS. 5, 6 and 7 show three further embodiments of the improved valve ofthe present invention. In FIG. 5, the valve 10' includes an annularmounting structure 40, similar to ring 12 of FIG. 1, which includes apair of opposed spaced rigid projections 42 with substantially arcuateterminal ends 44 formed as an integral part of the edge opposite thevalve orifice 43. Mounting structure 40 and projections 42 are coveredwith the same flexible non-resilient synthetic fabric described abovewith reference to the embodiment of FIGS. 1-4. It is now clear that theembodiment of FIG. 5 includes opposed flaps or wall segments 46 and 48(formed of the same flexible, non-resilient fabric described above)attached at their proximal ends 50 and 52 to annular mounting structure40 in the spaces between projections 42. Flaps 46 and and 48 andprojections 42 cooperate to form a tubular element having an internalflow passage analogous to tube 16. Magnetic members 54 and 56 which maybe of the repulsive force creating type are enclosed in the fabric ofwhich flaps 46 and 48 are constructed at the distal ends 57 and 59 offlaps 46 and 48, respectively. The valve of FIG. 5 does not utilize acentral tube like central tube 16 of FIGS. 1 through 4, but ratherrelies upon the sealing capability of ends 57 and 59 as well as thesealing capability of flaps 46 and 48 with respective edges of spacedprojections 42, as noted above. Projections 42 provide support means forflaps 46 and 48 so that when the valve is in a closed position, as shownin FIG. 5, magnetic members 54 and 56 rest on the terminal ends 44 ofprojections 42. Magnetic members 54 and 56 must be shaped so that theyfit tightly together at 58 and conform securely to the substantiallyarcuate terminal ends 44 of projections 42 to prevent fluid leakage whenthe valve is closed.

FIG. 6 illustrates a third valve embodiment 10" of the presentinvention. As in the other embodiments, valve 10" includes an annularmounting structure 60 which includes as an integral part of its upperedge opposite the valve orifice an opposed pair of spaced, rigidprojections 62. Each projection 62 includes two substantially arcuateprotrusions 64 on the downstream side of the annular structure 60.Annular structure 60 and projections 62 are covered with the flexiblefabric hereinbefore described which extends beyond ends 64 to form acentral tube 66. Opposed fabric flaps 68 and 70 are attached to annularmounting structure 60 in the spaces between projections 62 at 72 and 74.Flaps 68 and 70 include within their structure at the distal endsmagnetic members 76 and 78, which exert sufficient attractive orrepulsive force to operate in either the attractive force mode or therepulsive force mode described above with respect to the embodiment ofFIGS. 1-4. Flaps 68 and 70 are shown terminating short of end 80 ofcentral tube 66. End 80 represents the valve outlet in this embodiment.

Yet a fourth embodiment of the novelty structure of the presentinvention is shown in bottom view in FIG. 7A. The valve of thisembodiment, generally depicted at 82, provides an annular mountingstructure 84, covered with a ribbed, flexible fabric which has beenfolded to provide a raised ridge 86 along the outer edge of mountingring 84. Ridge 86 may be used as a suture collar to facilitateattachment of valve 82 to a body vessel. The flexible fabric covering onmounting ring 84 extends beyond mounting ring 84 to form a central tube88. In this embodiment, opposite sides of central tube 88 are attachedtogether at 89 to form a bifurcated passage. In FIG. 7A one of thebifurcated passages 90 is closed along line 90' by a portion of tube 88which extends downstream of point 89. The other bifurcated passage 92 issimilarly closed along line 92' along a downward section of tube 88. Theportion of tube 88 extending in the downward direction from point 89 isrejoined to form a single passage as illustrated in FIG. 7B wherein atop elevational view of the valve of FIG. 7A is illustrated.

As in the other embodiments hereinbefore described, opposed, spacedfabric flaps, 97 and 99, which include at their distal ends magneticmembers 101 and 103, are attached at their proximal ends to annularmounting structure 84.

The effects prior art valves have on blood flow in the aorta aredepicted in FIGS. 8 and 9A-9C and further demonstrate the advantages ofthe improved valve of the present invention already discussed. FIG. 8shows the normal linear flow of the blood at the location of the aorticvalve, illustrated schematically at 96, within aorta 102. The coronaryarteries are shown at 98 and the left ventricle at 100. Arrow 104represents the normal centralized flow of blood through the aorticvalve. FIG. 9A illustrates the placement of a prosthetic ball and cagevalve in the normal aortic valve position. The ball 106 is enclosedwithin a cage 108. As the blood flow, represented by arrows 104, leavesthe left ventricle 100, it passes into the valve, pushing the ball 106to the top of the cage 109. The flow is prevented from followinglinearly through the valve by the presence of the ball 106.Consequently, the blood flow is diverted around the ball 106 anddirected toward points 110 on the walls of the aorta 102, which createsturbulence in the blood and can result in damage to the blood cells. Inaddition, the pressure exerted by the blood hitting the walls of theaorta at 110 may also cause injury to the vessel wall. Yet anotherdisadvantage of this type of valve is the traumatic effect on the bloodcells of both the valve opening and closing. Because ball 106 movessolely in response to blood pressure differentials and flow, significantball velocity can develop as the ball moves between its open and closedpositions. This sudden impact of the ball against cage 108 upon openingand against the valve seat 109 upon closing can have a traumatic effecton the blood cells which are caught between the impacting surfaces. Theflexible tube-type valve of the present invention completely avoidsthese drawbacks of the prior art by providing centralized generallylaminar flow through a single or bifurcated valve passage having nopressure induced impacting of valve surfaces either upon opening orclosing of the valve. In FIG. 9B, a caged disc-type valve 112 ispositioned between the aorta 102 and the left ventricle 100. This typeof valve causes the same type of traumatic effect upon opening andclosing as does the ball and cage valve. Moreover, the blood flowthrough this type of valve, represented by arrows 104, is diverted bydisc 114, resulting in a semicentral flow of the blood with a minimalgradient. As with the ball and cage structure of FIG. 9A, the flow isalso directed toward the aortic walls and can cause injury at points110. Additionally, the flow of blood through valve 112 is marked byturbulence in the aorta near points 110, which can cause trauma to theblood cells. FIG. 9C further illustrates the problems encountered withanother type of prior art valve 116 employing a tilting disc 118 shownin the open position in the aortic valve position. Because the valveoperates in response to pressure differentials, blood cells may bedamaged by the impacting surfaces. Moreover, the blood flow, againrepresented by arrows 104, is diverted by disc 118 toward the aorticwalls, causing injury at points 110. The turbulence discussed above withits attendant blood cell damage and hemolysis are additional drawbacksto the effectiveness of this prior art valve. In its broader aspects,the present invention includes any means for using magnetic forces toprevent the impacting of valve surfaces caused by a differential inupstream and downstream pressures. It is thus within the scope of thisinvention to use the repulsive force induced between magnetic poleshaving the same polarity to avoid the impact which normally occurs inthe type of valves illustrated in FIGS. 9A through 9C when such valvesare opened or closed. For example, first and second magnetic elementscould be mounted within a disc valve 112 as shown in FIG. 9B such thatone pole of a first magnetic element mounted in disc 114 would generatea repulsive force with the same pole of the second magnetic elementmounted in the disc surround-cage of valve 112. By this arrangement, thetraumatic impact normally caused upon valve opening by the engagement ofdisc 114 with the surround cage can be entirely avoided.

Alternatively FIG. 10 illustrates another valve structure in whichmagnetic repulsive force is used to prevent traumatic impact of thevalve elements. In particular, FIG. 10 discloses a bi-valve 120 with aring-like mounting structure 122 similar to mounting structure 12 and apair of valve flaps 124 and 126 hinged along a diametrical line 128extending between opposite sides of ring-like mounting structure 122. Apair of permanent magnetic elements 130 and 132 are connected,respectively, with flaps 124 and 126 in a position to produce repulsiveforce whenever the flaps are moved together in a valve open position,such as illustrated by arrows 134. This repulsive force will tend toprevent traumatic and/or noise generating impact of the flaps 124 and126. When the upstream pressure P₁ is less than the downstream pressureP₂, flaps 124 and 126 will tend to close. The closure motion may beaided by the repulsive forces generated by magnetic elements 130 and132. As further illustrated in FIG. 10, the bi flap valve 120 mayinclude a second pair of permanent magnets 136 and 138 imbedded inring-like support structure 122 arranged to create a weak repulsiveforce to further prevent traumatic impact of flaps 124 and 126,respectively, with structure 122 upon closure of the valve. As disclosedin FIG. 10, each flap 124 and 126 acts as a stop for the other flap andring 122 acts as a stop for both. Magnetic elements 130, 132, 136 and138 together form valve impact preventing means for preventing traumaticimpact of the valve elements (flaps) with the stops. In the embodimentsof FIGS. 1-7, each side of the opposed wall segments similarly canoperate as a stop to the opposed wall segment and the magnetic elementpairs (28 and 30; 54 and 56; and 76 and 78) will operate as valve impactpreventing means when arranged to produce repulsive forces between oneanother as they are brought together.

APPLICATION AND OPERATION OF INVENTION

The preceding description of the improved valve of the present inventionis merely illustrative and is not meant to limit its application, it iscontemplated that the novel magnetically-assisted closing devicedescribed above could be used in any human or animal structure where asphincter type action is needed to open or close a structure or organ,especially where there is a naturally-occurring valve. The presentinvention could also be used as a valve in tubing connecting bodycavities or structures, such as in the pleural cavity or peritonealcavity. In addition, the improved valve could be used outside the bodyin medical equipment, such as respirators, which utilize valves tocontrol the flow of pulsatory fluids. Another application of theinvention concept presented herein lies in the modification of existingprosthetic valves. By way of example, magnetic members exerting arepulsive force could be provided at the tops of the cage struts in aball and cage type valve. The ball, which would be made of a materialresponsive to magnetic repulsive force, would be pushed against the cagein the open position by the pressure of the fluid entering the valve andrepelled from the cage by the repulsive magnetic force when the fluidpressure dropped, thus magnetically to assume a closed position, inwhich the ball is seated in the valve seat. This magnetically assistedclosing would reduce the amount of turbulence, hence the level of traumato the blood cells and hemolysis.

The operation of the improved valve of the present invention as it wouldfunction if used to replace the aortic valve in a human heart presents aconvenient illustration. The improved valve is placed in the aorticposition with valve orifice 32 toward the left ventricle and valveoutlet 26 of central tube 16 and flaps 18 and 20 extending into theaorta. During systole blood from the left ventricle flows into valveorifice 32 and into central tube 16, exerting sufficient pressurebetween magnetic members 28 and 30 so that they are forced apart,separating flaps 18 and 20 and permitting central tube 16 to expand toits largest diameter, as shown in in FIG. 3. During diastole, closing ofthe valve is initiated. Magnetic members 28 and 30 come together,compressing central tube 16 at 34 to close the valve. During diastolethe flexible valve portions 16, 18 and 20 disposed in response to thepressure gradient. The valve is then fully closed, as shown in FIG. 4,and ready to respond to another systolic/diastolic cycle.

Other aspects, objects and advantages of this invention can be obtainedfrom a study of the drawings, the disclosure and the appended claims.

I claim:
 1. A prosthetic valve for causing unidirectional flow of apulsatory fluid, comprising(a) mounting means positionable upstreamwithin the flow of pulsatory fluid for forming an inlet through whichthe pulsatory fluid may flow into the valve, (b) valve outlet means formoving from a first configuration in which fluid flow through said inletis cut off to a second configuration in which fluid may freely flowthrough said inlet from the upstream side to the downstream side of thevalve in response to the fluid pressure upstream of the valve increasingabove the fluid pressure downstream of the valve, said valve outletmeans including a valve element moving from a first position in whichsaid inlet is closed off when said valve outlet means is in said firstconfiguration and a second position in which said inlet is open forpassage of fluid therethrough when said valve outlet means is in saidsecond configuration, said valve outlet means further including a stopfor engaging said valve element in one of said positions, wherein saidstop includes opposed wall segments and said wall segments are extendedlaterally and are joined to form a tubular element, said joined wallsegments being formed of non-resilient, biologically non-reactivefabric; and (c) valve impact preventing means for preventing traumaticimpact of said valve element with said stop, said valve impactpreventing means including magnetic means for forming a magneticrepulsive force which tends to repel said valve element from said stopwith a force which increases as said valve element comes closer to saidstop.
 2. A valve as defined in claim 1, wherein said impact preventingmeans includes a pair of permanent magnets positioned on laterallyopposite sides adjacent the downstream end of said wall segments.
 3. Avalve as defined in claim 2, wherein said impact preventing meansincludes a pair of flexible non-resilient flaps connected at one end tosaid valve support means and at the other end to said pair of permanentmagnets, respectively.
 4. A valve as defined in claim 3, wherein saidtubular element includes an internal dividing web joining the opposedinside wall surfaces of said tubular element, said internal dividing webbeing positioned to form a bifurcated passage for fluid flow throughsaid tubular element when said valve outlet means is moved to saidsecond configuration.
 5. A valve as defined in claim 1, wherein saidtubular element includes a pair of rigid projections positioned onopposite sides of said mounting means and extending downstream betweensaid wall segments, said pair of rigid projections forming a sealingengagement with said wall segments when said valve outlet means is insaid first configuration, said impact preventing means including a pairof permanent magnets attached to the downstream ends of said wallsegments, respectively, and being arranged to provide a mutuallyrepulsive force tending to push said wall segments apart.
 6. A valve asdefined in claim 3, wherein said valve outlet means includes a pair ofrigid projections connected to opposed sides of said mounting means andextending in a downstream direction, said rigid projections providingsupport to said wall segments when said valve outlet means is in saidfirst configuration.
 7. A valve as defined in claim 6, wherein each saidrigid projection includes two substantially arcuate protrusions on thedownstream side.
 8. A valve as defined in claim 1, wherein said mountingmeans includes a semi-rigid ring and a fabric material covering at leastthe outside surface of said ring to provide a suture holding surface forretaining said valve when implanted.
 9. A prosthetic valve for causingunidirectional flow of a pulsatory fluid, comprising(a) mounting meanspositionable upstream within the flow of pulsatory fluid for forming aninlet through which the pulsatory fluid may flow into the valve, whereinsaid mounting means includes a ring-like mounting structure containingsaid inlet, (b) valve outlet means for moving from a first configurationin which fluid flow through said inlet is cut off to a secondconfiguration in which fluid may freely flow through said inlet from theupstream side to the downstream side of the valve in response to thefluid pressure upstream of the valve increasing above the fluid pressuredownstream of the valve, said valve outlet means including a valveelement moving from a first position in which said inlet is closed offwhen said valve outlet means is in said first configuration and a secondposition in which said inlet is open for passage of fluid therethroughwhen said valve outlet means is in said second configuration, said valveoutlet means further including a stop for engaging said valve element inone of said positions, wherein said valve element includes a pair offlaps mounted for pivotal movement around a common diametrical lineextending across said inlet between a first position in which fluidflowing through said inlet is cut off and a second position in whichfluid may freely flow through said inlet, and (c) valve impactpreventing means for preventing traumatic impact of said valve elementwith said stop, said valve impact preventing means including magneticmeans for forming a magnetic repulsive force which tends to repel saidvalve element from said stop with a force which increases as said valveelement comes closer to said stop, wherein said valve impact preventingmeans includes a pair of magnetic elements arranged to create repulsiveforce tending to move said flaps from said second position to said firstposition and wherein each flap operates as a stop to the other flap whenin the second position.
 10. A prosthetic valve as defined in claim 9,wherein said valve impact preventing means further includes a secondpair of permanent magnets connected with said support structure forcreating a repulsive force tending to move said flaps from said firstposition to said second position.